<?php

if (! defined('BASEPATH'))
    exit('No direct script access allowed');

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package CodeIgniter
 * @author ExpressionEngine Dev Team
 * @copyright Copyright (c) 2008 - 2011, EllisLab, Inc.
 * @license http://codeigniter.com/user_guide/license.html
 * @link http://codeigniter.com
 * @since Version 1.0
 * @filesource
 *
 */
    
// ------------------------------------------------------------------------

/**
 * Database Driver Class
 *
 * This is the platform-independent base DB implementation class.
 * This class will not be called directly. Rather, the adapter
 * class for the specific database will extend and instantiate it.
 *
 * @package CodeIgniter
 * @subpackage Drivers
 * @category Database
 * @author ExpressionEngine Dev Team
 * @link http://codeigniter.com/user_guide/database/
 */
class CI_DB_driver
{

    var $username;

    var $password;

    var $hostname;

    var $database;

    var $dbdriver = 'mysql';

    var $dbprefix = '';

    var $char_set = 'utf8';

    var $dbcollat = 'utf8_general_ci';

    var $autoinit = TRUE;
 // Whether to automatically initialize the DB
    var $swap_pre = '';

    var $port = '';

    var $pconnect = FALSE;

    var $conn_id = FALSE;

    var $result_id = FALSE;

    var $db_debug = FALSE;

    var $benchmark = 0;

    var $query_count = 0;

    var $bind_marker = '?';

    var $save_queries = TRUE;

    var $queries = array();

    var $query_times = array();

    var $data_cache = array();

    var $trans_enabled = TRUE;

    var $trans_strict = TRUE;

    var $_trans_depth = 0;

    var $_trans_status = TRUE;
 // Used with transactions to determine if a
                               // rollback should occur
    var $cache_on = FALSE;

    var $cachedir = '';

    var $cache_autodel = FALSE;

    var $CACHE;
 // The cache class object
                
    // Private variables
    var $_protect_identifiers = TRUE;

    var $_reserved_identifiers = array(
            '*'
    );
 // Identifiers that should NOT be
                                             // escaped
                                             
    // These are use with Oracle
    var $stmt_id;

    var $curs_id;

    var $limit_used;

    /**
     * Constructor.
     * Accepts one parameter containing the database
     * connection settings.
     *
     * @param
     *            array
     */
    function __construct ($params)
    {
        if (is_array($params)) {
            foreach ($params as $key => $val) {
                $this->$key = $val;
            }
        }
        
        log_message('debug', 'Database Driver Class Initialized');
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Initialize Database Settings
     *
     * @access private Called by the constructor
     * @param
     *            mixed
     * @return void
     */
    function initialize ()
    {
        // If an existing connection resource is available
        // there is no need to connect and select the database
        if (is_resource($this->conn_id) or is_object($this->conn_id)) {
            return TRUE;
        }
        
        // ----------------------------------------------------------------
        
        // Connect to the database and set the connection ID
        $this->conn_id = ($this->pconnect == FALSE) ? $this->db_connect() : $this->db_pconnect();
        
        // No connection resource? Throw an error
        if (! $this->conn_id) {
            log_message('error', 'Unable to connect to the database');
            
            if ($this->db_debug) {
                $this->display_error('db_unable_to_connect');
            }
            return FALSE;
        }
        
        // ----------------------------------------------------------------
        
        // Select the DB... assuming a database name is specified in the config
        // file
        if ($this->database != '') {
            if (! $this->db_select()) {
                log_message('error', 
                        'Unable to select database: ' . $this->database);
                
                if ($this->db_debug) {
                    $this->display_error('db_unable_to_select', $this->database);
                }
                return FALSE;
            } else {
                // We've selected the DB. Now we set the character set
                if (! $this->db_set_charset($this->char_set, $this->dbcollat)) {
                    return FALSE;
                }
                
                return TRUE;
            }
        }
        
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Set client character set
     *
     * @access public
     * @param
     *            string
     * @param
     *            string
     * @return resource
     */
    function db_set_charset ($charset, $collation)
    {
        if (! $this->_db_set_charset($this->char_set, $this->dbcollat)) {
            log_message('error', 
                    'Unable to set database connection charset: ' .
                             $this->char_set);
            
            if ($this->db_debug) {
                $this->display_error('db_unable_to_set_charset', 
                        $this->char_set);
            }
            
            return FALSE;
        }
        
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * The name of the platform in use (mysql, mssql, etc...)
     *
     * @access public
     * @return string
     */
    function platform ()
    {
        return $this->dbdriver;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Database Version Number.
     * Returns a string containing the
     * version of the database being used
     *
     * @access public
     * @return string
     */
    function version ()
    {
        if (FALSE === ($sql = $this->_version())) {
            if ($this->db_debug) {
                return $this->display_error('db_unsupported_function');
            }
            return FALSE;
        }
        
        // Some DBs have functions that return the version, and don't run
        // special
        // SQL queries per se. In these instances, just return the result.
        $driver_version_exceptions = array(
                'oci8',
                'sqlite',
                'cubrid'
        );
        
        if (in_array($this->dbdriver, $driver_version_exceptions)) {
            return $sql;
        } else {
            $query = $this->query($sql);
            return $query->row('ver');
        }
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Execute the query
     *
     * Accepts an SQL string as input and returns a result object upon
     * successful execution of a "read" type query. Returns boolean TRUE
     * upon successful execution of a "write" type query. Returns boolean
     * FALSE upon failure, and if the $db_debug variable is set to TRUE
     * will raise an error.
     *
     * @access public
     * @param
     *            string An SQL query string
     * @param
     *            array An array of binding data
     * @return mixed
     */
    function query ($sql, $binds = FALSE, $return_object = TRUE)
    {
        if ($sql == '') {
            if ($this->db_debug) {
                log_message('error', 'Invalid query: ' . $sql);
                return $this->display_error('db_invalid_query');
            }
            return FALSE;
        }
        
        // Verify table prefix and replace if necessary
        if (($this->dbprefix != '' and $this->swap_pre != '') and
                 ($this->dbprefix != $this->swap_pre)) {
            $sql = preg_replace("/(\W)" . $this->swap_pre . "(\S+?)/", 
                    "\\1" . $this->dbprefix . "\\2", $sql);
        }
        
        // Compile binds if needed
        if ($binds !== FALSE) {
            $sql = $this->compile_binds($sql, $binds);
        }
        
        // Is query caching enabled? If the query is a "read type"
        // we will load the caching class and return the previously
        // cached query if it exists
        if ($this->cache_on == TRUE and stristr($sql, 'SELECT')) {
            if ($this->_cache_init()) {
                $this->load_rdriver();
                if (FALSE !== ($cache = $this->CACHE->read($sql))) {
                    return $cache;
                }
            }
        }
        
        // Save the query for debugging
        if ($this->save_queries == TRUE) {
            $this->queries[] = $sql;
        }
        
        // Start the Query Timer
        $time_start = list ($sm, $ss) = explode(' ', microtime());
        
        // Run the Query
        if (FALSE === ($this->result_id = $this->simple_query($sql))) {
            if ($this->save_queries == TRUE) {
                $this->query_times[] = 0;
            }
            
            // This will trigger a rollback if transactions are being used
            $this->_trans_status = FALSE;
            
            if ($this->db_debug) {
                // grab the error number and message now, as we might run some
                // additional queries before displaying the error
                $error_no = $this->_error_number();
                $error_msg = $this->_error_message();
                
                // We call this function in order to roll-back queries
                // if transactions are enabled. If we don't call this here
                // the error message will trigger an exit, causing the
                // transactions to remain in limbo.
                $this->trans_complete();
                
                // Log and display errors
                log_message('error', 'Query error: ' . $error_msg);
                return $this->display_error(
                        array(
                                'Error Number: ' . $error_no,
                                $error_msg,
                                $sql
                        ));
            }
            
            return FALSE;
        }
        
        // Stop and aggregate the query time results
        $time_end = list ($em, $es) = explode(' ', microtime());
        $this->benchmark += ($em + $es) - ($sm + $ss);
        
        if ($this->save_queries == TRUE) {
            $this->query_times[] = ($em + $es) - ($sm + $ss);
        }
        
        // Increment the query counter
        $this->query_count ++;
        
        // Was the query a "write" type?
        // If so we'll simply return true
        if ($this->is_write_type($sql) === TRUE) {
            // If caching is enabled we'll auto-cleanup any
            // existing files related to this particular URI
            if ($this->cache_on == TRUE and $this->cache_autodel == TRUE and
                     $this->_cache_init()) {
                $this->CACHE->delete();
            }
            
            return TRUE;
        }
        
        // Return TRUE if we don't need to create a result object
        // Currently only the Oracle driver uses this when stored
        // procedures are used
        if ($return_object !== TRUE) {
            return TRUE;
        }
        
        // Load and instantiate the result driver
        
        $driver = $this->load_rdriver();
        $RES = new $driver();
        $RES->conn_id = $this->conn_id;
        $RES->result_id = $this->result_id;
        
        if ($this->dbdriver == 'oci8') {
            $RES->stmt_id = $this->stmt_id;
            $RES->curs_id = NULL;
            $RES->limit_used = $this->limit_used;
            $this->stmt_id = FALSE;
        }
        
        // oci8 vars must be set before calling this
        $RES->num_rows = $RES->num_rows();
        
        // Is query caching enabled? If so, we'll serialize the
        // result object and save it to a cache file.
        if ($this->cache_on == TRUE and $this->_cache_init()) {
            // We'll create a new instance of the result object
            // only without the platform specific driver since
            // we can't use it with cached data (the query result
            // resource ID won't be any good once we've cached the
            // result object, so we'll have to compile the data
            // and save it)
            $CR = new CI_DB_result();
            $CR->num_rows = $RES->num_rows();
            $CR->result_object = $RES->result_object();
            $CR->result_array = $RES->result_array();
            
            // Reset these since cached objects can not utilize resource IDs.
            $CR->conn_id = NULL;
            $CR->result_id = NULL;
            
            $this->CACHE->write($sql, $CR);
        }
        
        return $RES;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Load the result drivers
     *
     * @access public
     * @return string name of the result class
     */
    function load_rdriver ()
    {
        $driver = 'CI_DB_' . $this->dbdriver . '_result';
        
        if (! class_exists($driver)) {
            include_once (BASEPATH . 'database/DB_result.php');
            include_once (BASEPATH . 'database/drivers/' . $this->dbdriver . '/' .
                     $this->dbdriver . '_result.php');
        }
        
        return $driver;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Simple Query
     * This is a simplified version of the query() function.
     * Internally
     * we only use it when running transaction commands since they do
     * not require all the features of the main query() function.
     *
     * @access public
     * @param
     *            string the sql query
     * @return mixed
     */
    function simple_query ($sql)
    {
        if (! $this->conn_id) {
            $this->initialize();
        }
        
        return $this->_execute($sql);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Disable Transactions
     * This permits transactions to be disabled at run-time.
     *
     * @access public
     * @return void
     */
    function trans_off ()
    {
        $this->trans_enabled = FALSE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Enable/disable Transaction Strict Mode
     * When strict mode is enabled, if you are running multiple groups of
     * transactions, if one group fails all groups will be rolled back.
     * If strict mode is disabled, each group is treated autonomously, meaning
     * a failure of one group will not affect any others
     *
     * @access public
     * @return void
     */
    function trans_strict ($mode = TRUE)
    {
        $this->trans_strict = is_bool($mode) ? $mode : TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Start Transaction
     *
     * @access public
     * @return void
     */
    function trans_start ($test_mode = FALSE)
    {
        if (! $this->trans_enabled) {
            return FALSE;
        }
        
        // When transactions are nested we only begin/commit/rollback the
        // outermost ones
        if ($this->_trans_depth > 0) {
            $this->_trans_depth += 1;
            return;
        }
        
        $this->trans_begin($test_mode);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Complete Transaction
     *
     * @access public
     * @return bool
     */
    function trans_complete ()
    {
        if (! $this->trans_enabled) {
            return FALSE;
        }
        
        // When transactions are nested we only begin/commit/rollback the
        // outermost ones
        if ($this->_trans_depth > 1) {
            $this->_trans_depth -= 1;
            return TRUE;
        }
        
        // The query() function will set this flag to FALSE in the event that a
        // query failed
        if ($this->_trans_status === FALSE) {
            $this->trans_rollback();
            
            // If we are NOT running in strict mode, we will reset
            // the _trans_status flag so that subsequent groups of transactions
            // will be permitted.
            if ($this->trans_strict === FALSE) {
                $this->_trans_status = TRUE;
            }
            
            log_message('debug', 'DB Transaction Failure');
            return FALSE;
        }
        
        $this->trans_commit();
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Lets you retrieve the transaction flag to determine if it has failed
     *
     * @access public
     * @return bool
     */
    function trans_status ()
    {
        return $this->_trans_status;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Compile Bindings
     *
     * @access public
     * @param
     *            string the sql statement
     * @param
     *            array an array of bind data
     * @return string
     */
    function compile_binds ($sql, $binds)
    {
        if (strpos($sql, $this->bind_marker) === FALSE) {
            return $sql;
        }
        
        if (! is_array($binds)) {
            $binds = array(
                    $binds
            );
        }
        
        // Get the sql segments around the bind markers
        $segments = explode($this->bind_marker, $sql);
        
        // The count of bind should be 1 less then the count of segments
        // If there are more bind arguments trim it down
        if (count($binds) >= count($segments)) {
            $binds = array_slice($binds, 0, count($segments) - 1);
        }
        
        // Construct the binded query
        $result = $segments[0];
        $i = 0;
        foreach ($binds as $bind) {
            $result .= $this->escape($bind);
            $result .= $segments[++ $i];
        }
        
        return $result;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Determines if a query is a "write" type.
     *
     * @access public
     * @param
     *            string An SQL query string
     * @return boolean
     */
    function is_write_type ($sql)
    {
        if (! preg_match(
                '/^\s*"?(SET|INSERT|UPDATE|DELETE|REPLACE|CREATE|DROP|TRUNCATE|LOAD DATA|COPY|ALTER|GRANT|REVOKE|LOCK|UNLOCK)\s+/i', 
                $sql)) {
            return FALSE;
        }
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Calculate the aggregate query elapsed time
     *
     * @access public
     * @param
     *            integer The number of decimal places
     * @return integer
     */
    function elapsed_time ($decimals = 6)
    {
        return number_format($this->benchmark, $decimals);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Returns the total number of queries
     *
     * @access public
     * @return integer
     */
    function total_queries ()
    {
        return $this->query_count;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Returns the last query that was executed
     *
     * @access public
     * @return void
     */
    function last_query ()
    {
        return end($this->queries);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * "Smart" Escape String
     *
     * Escapes data based on type
     * Sets boolean and null types
     *
     * @access public
     * @param
     *            string
     * @return mixed
     */
    function escape ($str)
    {
        if (is_string($str)) {
            $str = "'" . $this->escape_str($str) . "'";
        } elseif (is_bool($str)) {
            $str = ($str === FALSE) ? 0 : 1;
        } elseif (is_null($str)) {
            $str = 'NULL';
        }
        
        return $str;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Escape LIKE String
     *
     * Calls the individual driver for platform
     * specific escaping for LIKE conditions
     *
     * @access public
     * @param
     *            string
     * @return mixed
     */
    function escape_like_str ($str)
    {
        return $this->escape_str($str, TRUE);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Primary
     *
     * Retrieves the primary key. It assumes that the row in the first
     * position is the primary key
     *
     * @access public
     * @param
     *            string the table name
     * @return string
     */
    function primary ($table = '')
    {
        $fields = $this->list_fields($table);
        
        if (! is_array($fields)) {
            return FALSE;
        }
        
        return current($fields);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Returns an array of table names
     *
     * @access public
     * @return array
     */
    function list_tables ($constrain_by_prefix = FALSE)
    {
        // Is there a cached result?
        if (isset($this->data_cache['table_names'])) {
            return $this->data_cache['table_names'];
        }
        
        if (FALSE === ($sql = $this->_list_tables($constrain_by_prefix))) {
            if ($this->db_debug) {
                return $this->display_error('db_unsupported_function');
            }
            return FALSE;
        }
        
        $retval = array();
        $query = $this->query($sql);
        
        if ($query->num_rows() > 0) {
            foreach ($query->result_array() as $row) {
                if (isset($row['TABLE_NAME'])) {
                    $retval[] = $row['TABLE_NAME'];
                } else {
                    $retval[] = array_shift($row);
                }
            }
        }
        
        $this->data_cache['table_names'] = $retval;
        return $this->data_cache['table_names'];
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Determine if a particular table exists
     * 
     * @access public
     * @return boolean
     */
    function table_exists ($table_name)
    {
        return (! in_array(
                $this->_protect_identifiers($table_name, TRUE, FALSE, FALSE), 
                $this->list_tables())) ? FALSE : TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Fetch MySQL Field Names
     *
     * @access public
     * @param
     *            string the table name
     * @return array
     */
    function list_fields ($table = '')
    {
        // Is there a cached result?
        if (isset($this->data_cache['field_names'][$table])) {
            return $this->data_cache['field_names'][$table];
        }
        
        if ($table == '') {
            if ($this->db_debug) {
                return $this->display_error('db_field_param_missing');
            }
            return FALSE;
        }
        
        if (FALSE === ($sql = $this->_list_columns($table))) {
            if ($this->db_debug) {
                return $this->display_error('db_unsupported_function');
            }
            return FALSE;
        }
        
        $query = $this->query($sql);
        
        $retval = array();
        foreach ($query->result_array() as $row) {
            if (isset($row['COLUMN_NAME'])) {
                $retval[] = $row['COLUMN_NAME'];
            } else {
                $retval[] = current($row);
            }
        }
        
        $this->data_cache['field_names'][$table] = $retval;
        return $this->data_cache['field_names'][$table];
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Determine if a particular field exists
     * 
     * @access public
     * @param
     *            string
     * @param
     *            string
     * @return boolean
     */
    function field_exists ($field_name, $table_name)
    {
        return (! in_array($field_name, $this->list_fields($table_name))) ? FALSE : TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Returns an object with field data
     *
     * @access public
     * @param
     *            string the table name
     * @return object
     */
    function field_data ($table = '')
    {
        if ($table == '') {
            if ($this->db_debug) {
                return $this->display_error('db_field_param_missing');
            }
            return FALSE;
        }
        
        $query = $this->query(
                $this->_field_data(
                        $this->_protect_identifiers($table, TRUE, NULL, FALSE)));
        
        return $query->field_data();
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Generate an insert string
     *
     * @access public
     * @param
     *            string the table upon which the query will be performed
     * @param
     *            array an associative array data of key/values
     * @return string
     */
    function insert_string ($table, $data)
    {
        $fields = array();
        $values = array();
        
        foreach ($data as $key => $val) {
            $fields[] = $this->_escape_identifiers($key);
            $values[] = $this->escape($val);
        }
        
        return $this->_insert(
                $this->_protect_identifiers($table, TRUE, NULL, FALSE), $fields, 
                $values);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Generate an update string
     *
     * @access public
     * @param
     *            string the table upon which the query will be performed
     * @param
     *            array an associative array data of key/values
     * @param
     *            mixed the "where" statement
     * @return string
     */
    function update_string ($table, $data, $where)
    {
        if ($where == '') {
            return false;
        }
        
        $fields = array();
        foreach ($data as $key => $val) {
            $fields[$this->_protect_identifiers($key)] = $this->escape($val);
        }
        
        if (! is_array($where)) {
            $dest = array(
                    $where
            );
        } else {
            $dest = array();
            foreach ($where as $key => $val) {
                $prefix = (count($dest) == 0) ? '' : ' AND ';
                
                if ($val !== '') {
                    if (! $this->_has_operator($key)) {
                        $key .= ' =';
                    }
                    
                    $val = ' ' . $this->escape($val);
                }
                
                $dest[] = $prefix . $key . $val;
            }
        }
        
        return $this->_update(
                $this->_protect_identifiers($table, TRUE, NULL, FALSE), $fields, 
                $dest);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Tests whether the string has an SQL operator
     *
     * @access private
     * @param
     *            string
     * @return bool
     */
    function _has_operator ($str)
    {
        $str = trim($str);
        if (! preg_match("/(\s|<|>|!|=|is null|is not null)/i", $str)) {
            return FALSE;
        }
        
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Enables a native PHP function to be run, using a platform agnostic
     * wrapper.
     *
     * @access public
     * @param
     *            string the function name
     * @param
     *            mixed any parameters needed by the function
     * @return mixed
     */
    function call_function ($function)
    {
        $driver = ($this->dbdriver == 'postgre') ? 'pg_' : $this->dbdriver . '_';
        
        if (FALSE === strpos($driver, $function)) {
            $function = $driver . $function;
        }
        
        if (! function_exists($function)) {
            if ($this->db_debug) {
                return $this->display_error('db_unsupported_function');
            }
            return FALSE;
        } else {
            $args = (func_num_args() > 1) ? array_splice(func_get_args(), 1) : null;
            if (is_null($args)) {
                return call_user_func($function);
            } else {
                return call_user_func_array($function, $args);
            }
        }
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Set Cache Directory Path
     *
     * @access public
     * @param
     *            string the path to the cache directory
     * @return void
     */
    function cache_set_path ($path = '')
    {
        $this->cachedir = $path;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Enable Query Caching
     *
     * @access public
     * @return void
     */
    function cache_on ()
    {
        $this->cache_on = TRUE;
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Disable Query Caching
     *
     * @access public
     * @return void
     */
    function cache_off ()
    {
        $this->cache_on = FALSE;
        return FALSE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Delete the cache files associated with a particular URI
     *
     * @access public
     * @return void
     */
    function cache_delete ($segment_one = '', $segment_two = '')
    {
        if (! $this->_cache_init()) {
            return FALSE;
        }
        return $this->CACHE->delete($segment_one, $segment_two);
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Delete All cache files
     *
     * @access public
     * @return void
     */
    function cache_delete_all ()
    {
        if (! $this->_cache_init()) {
            return FALSE;
        }
        
        return $this->CACHE->delete_all();
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Initialize the Cache Class
     *
     * @access private
     * @return void
     */
    function _cache_init ()
    {
        if (is_object($this->CACHE) and class_exists('CI_DB_Cache')) {
            return TRUE;
        }
        
        if (! class_exists('CI_DB_Cache')) {
            if (! @include (BASEPATH . 'database/DB_cache.php')) {
                return $this->cache_off();
            }
        }
        
        $this->CACHE = new CI_DB_Cache($this); // pass db object to support
                                               // multiple db connections and
                                               // returned db objects
        return TRUE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Close DB Connection
     *
     * @access public
     * @return void
     */
    function close ()
    {
        if (is_resource($this->conn_id) or is_object($this->conn_id)) {
            $this->_close($this->conn_id);
        }
        $this->conn_id = FALSE;
    }
    
    // --------------------------------------------------------------------
    
    /**
     * Display an error message
     *
     * @access public
     * @param
     *            string the error message
     * @param
     *            string any "swap" values
     * @param
     *            boolean whether to localize the message
     * @return string the application/error_db.php template
     */
    function display_error ($error = '', $swap = '', $native = FALSE)
    {
        $LANG = & load_class('Lang', 'core');
        $LANG->load('db');
        
        $heading = $LANG->line('db_error_heading');
        
        if ($native == TRUE) {
            $message = $error;
        } else {
            $message = (! is_array($error)) ? array(
                    str_replace('%s', $swap, $LANG->line($error))
            ) : $error;
        }
        
        // Find the most likely culprit of the error by going through
        // the backtrace until the source file is no longer in the
        // database folder.
        
        $trace = debug_backtrace();
        
        foreach ($trace as $call) {
            if (isset($call['file']) &&
                     strpos($call['file'], BASEPATH . 'database') === FALSE) {
                // Found it - use a relative path for safety
                $message[] = 'Filename: ' .
                 str_replace(array(
                        BASEPATH,
                        APPPATH
                ), '', $call['file']);
        $message[] = 'Line Number: ' . $call['line'];
        
        break;
    }
}

$error = & load_class('Exceptions', 'core');
echo $error->show_error($heading, $message, 'error_db');
exit();
}

// --------------------------------------------------------------------

/**
 * Protect Identifiers
 *
 * This function adds backticks if appropriate based on db type
 *
 * @access private
 * @param
 *            mixed the item to escape
 * @return mixed item with backticks
 */
function protect_identifiers ($item, $prefix_single = FALSE)
{
return $this->_protect_identifiers($item, $prefix_single);
}

// --------------------------------------------------------------------

/**
 * Protect Identifiers
 *
 * This function is used extensively by the Active Record class, and by
 * a couple functions in this class.
 * It takes a column or table name (optionally with an alias) and inserts
 * the table prefix onto it. Some logic is necessary in order to deal with
 * column names that include the path. Consider a query like this:
 *
 * SELECT * FROM hostname.database.table.column AS c FROM
 * hostname.database.table
 *
 * Or a query with aliasing:
 *
 * SELECT m.member_id, m.member_name FROM members AS m
 *
 * Since the column name can include up to four segments (host, DB, table,
 * column)
 * or also have an alias prefix, we need to do a bit of work to figure this out
 * and
 * insert the table prefix (if it exists) in the proper position, and escape
 * only
 * the correct identifiers.
 *
 * @access private
 * @param
 *            string
 * @param
 *            bool
 * @param
 *            mixed
 * @param
 *            bool
 * @return string
 */
function _protect_identifiers ($item, $prefix_single = FALSE, 
    $protect_identifiers = NULL, $field_exists = TRUE)
{
if (! is_bool($protect_identifiers)) {
    $protect_identifiers = $this->_protect_identifiers;
}

if (is_array($item)) {
    $escaped_array = array();
    
    foreach ($item as $k => $v) {
        $escaped_array[$this->_protect_identifiers($k)] = $this->_protect_identifiers(
                $v);
    }
    
    return $escaped_array;
}

// Convert tabs or multiple spaces into single spaces
$item = preg_replace('/[\t ]+/', ' ', $item);

// If the item has an alias declaration we remove it and set it aside.
// Basically we remove everything to the right of the first space
if (strpos($item, ' ') !== FALSE) {
    $alias = strstr($item, ' ');
    $item = substr($item, 0, - strlen($alias));
} else {
    $alias = '';
}

// This is basically a bug fix for queries that use MAX, MIN, etc.
// If a parenthesis is found we know that we do not need to
// escape the data or add a prefix. There's probably a more graceful
// way to deal with this, but I'm not thinking of it -- Rick
if (strpos($item, '(') !== FALSE) {
    return $item . $alias;
}

// Break the string apart if it contains periods, then insert the table prefix
// in the correct location, assuming the period doesn't indicate that we're
// dealing
// with an alias. While we're at it, we will escape the components
if (strpos($item, '.') !== FALSE) {
    $parts = explode('.', $item);
    
    // Does the first segment of the exploded item match
    // one of the aliases previously identified? If so,
    // we have nothing more to do other than escape the item
    if (in_array($parts[0], $this->ar_aliased_tables)) {
        if ($protect_identifiers === TRUE) {
            foreach ($parts as $key => $val) {
                if (! in_array($val, $this->_reserved_identifiers)) {
                    $parts[$key] = $this->_escape_identifiers($val);
                }
            }
            
            $item = implode('.', $parts);
        }
        return $item . $alias;
    }
    
    // Is there a table prefix defined in the config file? If not, no need to do
    // anything
    if ($this->dbprefix != '') {
        // We now add the table prefix based on some logic.
        // Do we have 4 segments (hostname.database.table.column)?
        // If so, we add the table prefix to the column name in the 3rd segment.
        if (isset($parts[3])) {
            $i = 2;
        }        // Do we have 3 segments (database.table.column)?
        // If so, we add the table prefix to the column name in 2nd position
        elseif (isset($parts[2])) {
            $i = 1;
        }         // Do we have 2 segments (table.column)?
        // If so, we add the table prefix to the column name in 1st segment
        else {
            $i = 0;
        }
        
        // This flag is set when the supplied $item does not contain a field
        // name.
        // This can happen when this function is being called from a JOIN.
        if ($field_exists == FALSE) {
            $i ++;
        }
        
        // Verify table prefix and replace if necessary
        if ($this->swap_pre != '' &&
                 strncmp($parts[$i], $this->swap_pre, strlen($this->swap_pre)) ===
                 0) {
            $parts[$i] = preg_replace("/^" . $this->swap_pre . "(\S+?)/", 
                    $this->dbprefix . "\\1", $parts[$i]);
        }
        
        // We only add the table prefix if it does not already exist
        if (substr($parts[$i], 0, strlen($this->dbprefix)) != $this->dbprefix) {
            $parts[$i] = $this->dbprefix . $parts[$i];
        }
        
        // Put the parts back together
        $item = implode('.', $parts);
    }
    
    if ($protect_identifiers === TRUE) {
        $item = $this->_escape_identifiers($item);
    }
    
    return $item . $alias;
}

// Is there a table prefix? If not, no need to insert it
if ($this->dbprefix != '') {
    // Verify table prefix and replace if necessary
    if ($this->swap_pre != '' &&
             strncmp($item, $this->swap_pre, strlen($this->swap_pre)) === 0) {
        $item = preg_replace("/^" . $this->swap_pre . "(\S+?)/", 
                $this->dbprefix . "\\1", $item);
    }
    
    // Do we prefix an item with no segments?
    if ($prefix_single == TRUE and
             substr($item, 0, strlen($this->dbprefix)) != $this->dbprefix) {
        $item = $this->dbprefix . $item;
    }
}

if ($protect_identifiers === TRUE and
         ! in_array($item, $this->_reserved_identifiers)) {
    $item = $this->_escape_identifiers($item);
}

return $item . $alias;
}

// --------------------------------------------------------------------

/**
 * Dummy method that allows Active Record class to be disabled
 *
 * This function is used extensively by every db driver.
 *
 * @return void
 */
protected function _reset_select ()
{}
}

/* End of file DB_driver.php */
/* Location: ./system/database/DB_driver.php */